Tritium Transport in Fluoride-Salt Cooled High Temperature ......Tritium Transport in Fluoride-Salt...

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Tritium Transport in Fluoride-Salt Cooled High Temperature Reactors (FHR) Raluca O. Scarlat Nuclear Engineering, UW Madison [email protected] | HEATandMass.ep.wisc.edu Idaho National Laboratory 20 August2015 FOR PUBLIC DISTRIBUTION

Transcript of Tritium Transport in Fluoride-Salt Cooled High Temperature ......Tritium Transport in Fluoride-Salt...

Page 1: Tritium Transport in Fluoride-Salt Cooled High Temperature ......Tritium Transport in Fluoride-Salt Cooled High Temperature Reactors (FHR) Raluca O. Scarlat Nuclear Engineering, UW

Tritium Transport in Fluoride-Salt Cooled High Temperature Reactors (FHR)

Raluca O. Scarlat

Nuclear Engineering, UW Madison [email protected] | HEATandMass.ep.wisc.edu

Idaho National Laboratory

20 August2015

FOR PUBLIC DISTRIBUTION

Page 2: Tritium Transport in Fluoride-Salt Cooled High Temperature ......Tritium Transport in Fluoride-Salt Cooled High Temperature Reactors (FHR) Raluca O. Scarlat Nuclear Engineering, UW

Outline

1.  Overview of FHR technology 2.  Tritium management in the FHR 3.  Tritium transport in the salt-graphite system 4.  Future work

Raluca Scarlat | HEATandMASS.ep.wisc.edu 2

Page 3: Tritium Transport in Fluoride-Salt Cooled High Temperature ......Tritium Transport in Fluoride-Salt Cooled High Temperature Reactors (FHR) Raluca O. Scarlat Nuclear Engineering, UW

FHRs: Solid Fuel, Salt Cooled Reactors

Liquid fluoride salt coolantsExcellent heat transferTransparent, clean fluoride saltBoiling point ~1400ºCReacts very slowly in airNo energy source to pressurize containmentBut high freezing temperature (459oC)And industrial safety required for Be

FHRs have uniquely large fuel thermal margin

Coated particle fuel(TRISO Fuel)

Raluca Scarlat | HEATandMASS.ep.wisc.edu 3

Page 4: Tritium Transport in Fluoride-Salt Cooled High Temperature ......Tritium Transport in Fluoride-Salt Cooled High Temperature Reactors (FHR) Raluca O. Scarlat Nuclear Engineering, UW

900 MWthPB-FHR

400 MWthPBMR

Page 5: Tritium Transport in Fluoride-Salt Cooled High Temperature ......Tritium Transport in Fluoride-Salt Cooled High Temperature Reactors (FHR) Raluca O. Scarlat Nuclear Engineering, UW

Nuclear Air-Brayton Combined Cycle (NACC)

!Aircraft Reactor Experiment, 1954

Fluoride Salt Coolants Were Developed

for the Aircraft Nuclear Propulsion Program

Conventional combined cycle gas plants achieve efficiencies of 50-60%

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Nuclear Air-Brayton Combined Cycle (NACC)

Modified GE 7FA Turbine for Co-fired NACC Base-load power: 42% efficiency (100 MWe) Gas co-firing: 66% efficiency (242 MWe)

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FHR Physical Plant Arrangement

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Coiled Tube Air Heaters (CTAHs)

P.V. Gilli et al., “Radial Flow Heat Exchanger,” U.S. Patent Number 3712370, Filing date: Sept. 22, 1970, Issue date: 1973

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PB-FHR Mark 1 Core Design

Andreades, C., Cisneros, A. T., Choi, J. K., Chong, A. Y. K., Fratoni, M., Hong, S., … Peterson, P. F. (2014). Technical Description of the “Mark 1” Pebble-Bed Fluoride-Salt-Cooled High-Temperature Reactor (PB-FHR) Power Plant.

Page 10: Tritium Transport in Fluoride-Salt Cooled High Temperature ......Tritium Transport in Fluoride-Salt Cooled High Temperature Reactors (FHR) Raluca O. Scarlat Nuclear Engineering, UW

Outline

1.  Overview of FHR technology 2.  Tritium management in the FHR 3.  Tritium transport in the salt-graphite system 4.  Future work

Raluca Scarlat | HEATandMASS.ep.wisc.edu 10

Page 11: Tritium Transport in Fluoride-Salt Cooled High Temperature ......Tritium Transport in Fluoride-Salt Cooled High Temperature Reactors (FHR) Raluca O. Scarlat Nuclear Engineering, UW

Tritium Source Term !  The main sources of tritium production are Li-6 and Li-7

!  Natural Li isotopic composition: 7.5% 6Li – 92.5% 7Li !  Target 6Li start-up concentration: 60 ppm 6Li !  Steady state 6Li concentration: 8 ppm 6Li

!  Lithium-6 is continuously created:

!  Natural Be isotopic composition: 100% 9Be

HeHLin 42

31

63

10 +→+ HnHenLi 3

110

42

10

73 ++→+

HeHeBen 42

62

94

10 +→+ eLiHe 0

163

62 −+→

0.0001$

0.001$

0.01$

0.1$

1$

10$

100$

1000$

10000$

0.00001$ 0.0001$ 0.001$ 0.01$ 0.1$ 1$ 10$ 100$ 1000$ 10000$ 100000$ 1000000$10000000$

Cross%S

ec)on%

(b)%

Energy%(eV)%

Cross Sections for (n,α) Reactions

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1.  http://www.nrc.gov/reactors/operating/ops-experience/tritium/faqs.html#normal 2.  Ohashi, Hirofumi and Sherman, Steven R. Tritium Movement and Accumulation in the NGNP System Interface and Hydrogen Plant. s.l. : Idaho National Laboratory,

2007. INL/EXT-07-12746

g/year per GWe Ci/year per GWePB-FHR 176 1.7 x 106

PWR (average) 0.08 0.73 x 103

CANDU (Darlington) 576 8.0 x 106

PBMR 512 4.9 x 106

MSR 92 0.65 x 106

Tritium Source Term

0.00 0.02 0.04 0.06 0.08 0.10 0.12 0.14 0.16 0.18

0 2 4 6 8

10 12 14

0 1 2 3 4 5 6 7 8 9 10 11

(mol

T/E

FPD

)

Triti

um P

rodu

ctio

n R

ate

(Ci/

EFP

Y)

Effective Full Power Years

Estimated Tritum Production Rate in the Mk1 PB-FHR Core

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FHR Tritium Emission Target

(Based on tritium production at steady state flibe isotopic composition, per GWe) !  FHR production: (1.7)106 Ci/yr (176 g/yr) !  If 100% released to air: 10-5 Ci/kg air (0.5x10-7 NRC limit)

!  Reduce by a factor of 200 !  PWR emissions: (0.7)103 Ci/yr (0.075 g/yr)

!  Reduce by a factor of 2000

Ohashi, Hirofumi and Sherman, Steven R. Tritium Movement and Accumulation in the NGNP System Interface and Hydrogen Plant. s.l. : Idaho National Laboratory, 2007. INL/EXT-07-12746

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Tritium Sinks and Sources

14 Raluca Scarlat | HEATandMASS.ep.wisc.edu

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Alternative Tritium Sinks

!  Fuel elements (pebbles: 100 days to full BU) !  Reflector pebbles !  Graphite particle absorber: annular cartridges of ~2.0-mm

carbon spheres !  Gas sparging !  Double-wall heat exchangers !  Membrane separation system

Page 16: Tritium Transport in Fluoride-Salt Cooled High Temperature ......Tritium Transport in Fluoride-Salt Cooled High Temperature Reactors (FHR) Raluca O. Scarlat Nuclear Engineering, UW

Tritium Permeation Barriers for CTAH tubes

Barrier Base Metal PRF

Al2O3

SS316, MANET, TZM, Ni,

Hastalloy-X

10 to >10,000

TiC, TiN, TiO2

SS316, MANET, TZM, Ti

3 to >10,000

Cr2O3 SS316 10 to 100Si Steels 10

BN 304SS 100N Fe 10 to 20

Er2O3 Steels 40 to 700

1.  Fluoride-Salt-Cooled High Temperature Reactor (FHR) Materials, Fuels and Components White Paper. UCBTH-12-003. Berkeley, CA. fhr.nuc.berkeley.edu

Barriers to release through CTAH•  4x lower mass convection coefficient than the pebble bed•  Aluminum Oxide Tritium permeation barrier: Kanthal AF or Alkrothal 14; ~0.1 mm•  Ensure low tritium concentration in the flibe at CTAH inlet: 10-12 to 10-23 wt

fraction (10-5 to 10-17 g/m3)

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SINAP Gas Sparging Studies

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Page 18: Tritium Transport in Fluoride-Salt Cooled High Temperature ......Tritium Transport in Fluoride-Salt Cooled High Temperature Reactors (FHR) Raluca O. Scarlat Nuclear Engineering, UW

Outline

1.  Overview of FHR technology 2.  Tritium management in the FHR 3.  Tritium transport in the salt-graphite system 4.  Future work

Raluca Scarlat | HEATandMASS.ep.wisc.edu 18

Page 19: Tritium Transport in Fluoride-Salt Cooled High Temperature ......Tritium Transport in Fluoride-Salt Cooled High Temperature Reactors (FHR) Raluca O. Scarlat Nuclear Engineering, UW

Tritium Transport Scales of Interest

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Core Fuel Element

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Perfect Sink Calculations

20 Raluca Scarlat | HEATandMASS.ep.wisc.edu

Table I. Perfect Sink Calculation Input and Outputs Inputs Inputs

Parameter Value Units Parameter Value Units Salt Average Temperature 923.15 K Carbon Molecular

Weight 12 g/mol

Reynolds Number 500 - Tritium Molecular Weight 3 g/mol

Diffusivity (Tritium in FLiBe) 3.90E-09 m2/s Graphite Density 1.70E+06 g/m3

Pebble Diameter 0.03 m Pebble Life 1.4 yr Salt Viscosity 6.78E-03 kg/(m*s) FLiBe Volume 46.82 m3

Salt Density 1.96E+03 kg/m3 Outputs

Salt Kinematic Viscosity 3.45E-06 m2/s Mass Transfer Coefficient 5.74E-05 m/s

Schmidt Number (ν/D) 885.25 - Bulk Salt

Concentration Steady State

2.38E-06 mol/m3

Steady State Production Rate 2.66E-07 mol/s

Bulk Salt Concentration

Startup 1.15E-05 mol/m3

Startup Production Rate 1.28E-06 mol/s Graphite Saturation Steady State 0.27 μg T/g C

Pebble Surface Area 1945.27 m2 Graphite Saturation Startup 1.28 μg T/g C

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Background Information: MSRE

!  ORNL-4865: Graphite stringers (CGB) from MSRE were analyzed for tritium with depth profiling. Contains information on FP distributions and transport.

!  ORNL-5011: Small graphite samples were exposed to T2 gas and analyzed.

!  Briggs (1972): Measured and calculated distributions of tritium in the MSRE.

!  Does this data lend itself to useful benchmark exercises?

!  If so, what assumptions about the MSRE and its operations limit application to FHR?

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What data is relevant?

!  750 C for 6.5 hr in P_T2 = 0.14 Pa on 1 cm^3 specimens.

!  POCO AXF-5Q graphite taken as the example (non-oxidized).

22 Michael Young

Strehlow, R. A. (1986). Chemisorption of tritium on graphites at elevated temperatures. Journal of Vacuum Science & Technology A: Vacuum, Surfaces, and Films, 4(1986), 1183. doi:10.1116/1.573434

Page 23: Tritium Transport in Fluoride-Salt Cooled High Temperature ......Tritium Transport in Fluoride-Salt Cooled High Temperature Reactors (FHR) Raluca O. Scarlat Nuclear Engineering, UW

Transport Mechanisms in Graphite Quentin Deslot and Michael Young

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!  In Graphite, a complex mechanism: - Both TF and T2 can diffuse - Diffusion: 3 Paths - Solubility: Chemisorption on several Traps

Quentin Deslot

Graphite structure and mechanism for tritium diffusion and trapping in graphite, from Atsumi

C•      +    T↓gas     →    C−T

Page 24: Tritium Transport in Fluoride-Salt Cooled High Temperature ......Tritium Transport in Fluoride-Salt Cooled High Temperature Reactors (FHR) Raluca O. Scarlat Nuclear Engineering, UW

Modeling of MSRE Depth Profile

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Trapping Model

Page 25: Tritium Transport in Fluoride-Salt Cooled High Temperature ......Tritium Transport in Fluoride-Salt Cooled High Temperature Reactors (FHR) Raluca O. Scarlat Nuclear Engineering, UW

Matrix Graphite and Nuclear Graphite

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Page 26: Tritium Transport in Fluoride-Salt Cooled High Temperature ......Tritium Transport in Fluoride-Salt Cooled High Temperature Reactors (FHR) Raluca O. Scarlat Nuclear Engineering, UW

Irradiation Effects

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Page 27: Tritium Transport in Fluoride-Salt Cooled High Temperature ......Tritium Transport in Fluoride-Salt Cooled High Temperature Reactors (FHR) Raluca O. Scarlat Nuclear Engineering, UW

!  Two in-core irradiations completed: 300 and 1000 hours at 700°C !  Double-encapsulation with nickel inner vessel,

graphite liner, titanium cold-wall !  100-300g of MSRE secondary flibe !  Nuclear heating with ±3°C temperature control

(He/Ne) !  Separate gas flows in each containment, tritium

collected

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MITR FHR Irradiations

" Future irradiations for IRP-2 o  Tritium uptake from flibe into irradiated

graphite (reflector, fuel matrix, etc.) o  Transport and release of gaseous tritium and

activation products (from flibe and corrosion) o  Tritium diffusion from salt through metals

(heat exchangers) o  Incorporate electrical heating for temperature

control independent of reactor power

Page 28: Tritium Transport in Fluoride-Salt Cooled High Temperature ......Tritium Transport in Fluoride-Salt Cooled High Temperature Reactors (FHR) Raluca O. Scarlat Nuclear Engineering, UW

Proposed Work

!  Goals: !  How much tritium will be retained in an FHR fuel pebble? !  How long will it take for the pebble to reach equilibrium tritium concentration?

!  Studies: !  What is the mechanism of tritium transport and trapping in matrix graphite? !  What data from nuclear graphite is relevant? !  What data from higher temperature is relevant? !  Characterize irradiation effects !  What is the effect of salt intrusion? !  What are the desorption characteristics – important for fuel handing

!  Ongoing Experiments 1.  Salt intrusion experiment 2.  Contact angle measurements 3.  Hydrogen absorption experiment 4.  Electrochemical impedance spectroscopy – 2015 NEUP Grant

28 Michael Young

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Electrochmical Techniques in Flibe Francesco Carotti

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Jenkins et al. 1968

Used by: Dr.Straka et al. at UJV (Czech Republic)

Problems:•  Never used for more than 80hrs•  Reaction of Ni2+ ions with

boron nitrite (important at low concentrations)

•  LaF3 difficult to machine? Expensive? Fragile?

Page 30: Tritium Transport in Fluoride-Salt Cooled High Temperature ......Tritium Transport in Fluoride-Salt Cooled High Temperature Reactors (FHR) Raluca O. Scarlat Nuclear Engineering, UW

Flibe Intrusion in Graphite Nisarg Patel and Huali Wu

30 Raluca Scarlat | HEATandMASS.ep.wisc.edu

0

500

1000

1500

2000

2500

-0.25 0.25 0.75 1.25 1.75 2.25 2.75 3.25

mg/

kg [p

pm w

t]

Micrometers

Li (With Salt)

-1000.000

0.000

1000.000

2000.000

3000.000

4000.000

0 101 201 302 402 503

F pp

mw

t

Depth in microns

F vs depth

F ppmwt

detection limit

GDMS Results Matrix Graphite Characterization

Electron Microprobe Results

Page 31: Tritium Transport in Fluoride-Salt Cooled High Temperature ......Tritium Transport in Fluoride-Salt Cooled High Temperature Reactors (FHR) Raluca O. Scarlat Nuclear Engineering, UW

Flibe Intrusion in Graphite Nisarg Patel and Huali Wu

31 Raluca Scarlat | HEATandMASS.ep.wisc.edu

0

500

1000

1500

2000

2500

-0.25 0.25 0.75 1.25 1.75 2.25 2.75 3.25

mg/

kg [p

pm w

t]

Micrometers

Li (With Salt)

-1000.000

0.000

1000.000

2000.000

3000.000

4000.000

0 101 201 302 402 503

F pp

mw

t

Depth in microns

F vs depth

F ppmwt

detection limit

Electron Microprobe Results Matrix Graphite Characterization

Page 32: Tritium Transport in Fluoride-Salt Cooled High Temperature ......Tritium Transport in Fluoride-Salt Cooled High Temperature Reactors (FHR) Raluca O. Scarlat Nuclear Engineering, UW

Proposed Work

!  Goals: !  How much tritium will be retained in an FHR fuel pebble? !  How long will it take for the pebble to reach equilibrium tritium concentration?

!  Ongoing Experiments 1.  Salt intrusion experiment 2.  Contact angle measurements 3.  Hydrogen absorption experiment 4.  Electrochemical impedance spectroscopy – 2015 NEUP Grant

32 Michael Young

Page 33: Tritium Transport in Fluoride-Salt Cooled High Temperature ......Tritium Transport in Fluoride-Salt Cooled High Temperature Reactors (FHR) Raluca O. Scarlat Nuclear Engineering, UW

Tritium Transport in Fluoride-Salt Cooled High Temperature Reactors (FHR)

Raluca O. Scarlat

Nuclear Engineering, UW Madison [email protected] | HEATandMass.ep.wisc.edu

Materials Science and Technology Division Seminar

Oak Ridge National Laboratory 20 March 2015